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The experimental setup accurately mimics the conditions in the non-linear dose controller without incorporating the additional hassles of a large stock tank, constant head tank and entrance tank. The As seen in Figure 1, the water circulates through a peristaltic pump to a small one liter reservoir intended to steady the pulsing input from the pump. The reservoir is connected to a tee, which connects a pressure sensor to the system just before the orifice. Water then drips through the smallest orifice, 0.1 cm diameter, into another one liter reservoir. The reservoir is connected to the pump, creating a closed system. The pump will be set to pump discharge water at the same rate as the water flows through the orifice to maintain steady-state operation. The experiment will first be run with deionized water as a control. Then it will be run with the maximum concentration of alum to be used in a plant, 125 g/L. As the experiment runs, Process Controller will record the pressure directly upstream of the orifice. If the orifice clogs, the pressure will increase significantly and Process Controller will turn off the pump to prevent any damageThe safety sensor is there as further validation of the presence of a clog. As the pressure from sensor 1 increases due to a clog, the pressure from sensor 2 decreases.
Results
First, a control experiment, using water, was performed to allow us to see normal pressure readings without any clog being present. These pressure readings will serve as a basis for comparison when we begin to run alum through our system. The pressure results from pressure sensor 1 can be seen in the graph below.
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The .1 cm orifice appeared to clog after 4 hours, indicating that a larger dosing orifice might need to be used. Further testing will need to be performed in order to verify these results, and determine the clog time for any larger orifice we select. An ideal system would only require cleaning once a day.
Since lab grade alum was utilized in this experiment and a clog was still present,the presence of foreign material, might not be the main cause of the clogs present in the Honduran plants. An inline strainer would still be recommended for future dosing systems, yet it should be noted that this won't eliminate the occurrence of clogs.